lightning strike damage
some years ago flying a similar type to the metroliner, descending into a major European airport whose controllers were well known for advising aircraft if they were flying towards an area of "radar intense returns" we suffered 2 lightning strikes inside 1 minute. Nothing at all showing on our or their radar, no turbulence ,very little precipitation and the cloud through which we were descending was a stratus type . Damage was a small hole in the starboard aileron (entry point) and the complete wingtip disappeared (exit point), lots of wires hanging down etc. Second strike blew the autopilot, most of the radios and the radar. Landed ok but just shows doesn't always happen when you expect it. Concentrates the mind a bit though!